President Obama spoke from the White House shortly after 6 p.m., saying that he and the First Lady sent their “deepest thoughts and prayers” to the victims.

“We don’t yet have all the answers,” he said. “We do know multiple people have been wounded, some gravely, in explosions at the Boston Marathon.”

Obama said he has reached out to the leaders of both parties, saying all are “united in concern for our fellow citizens.”

He praised the first responders and others who responded to the explosions.

“We still do not know who did this or why,” he said. But he added, ”Make no mistake, we will get to the bottom of this.”

Obama also went on to say: ”We will find out who did this, and we will hold them accountable.”

The American people will pray for Boston tonight, Obama said.

“I’m supremely confident that Bostonians will pull together, take care of each other and move forward,” he said.